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What's inside Optrex Eye Wash

This article was taken from the December issue of Wired magazine. Be the first to read Wired's articles in print before they're posted online, and get your hands on loads of additional content bysubscribing online

Each month Wired's chemist Dr John Emsley, author of nine books and 110 research papers, deconstructs and everyday product. This month: Optrex

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&gt; Benzalkonium chloride

BORIC ACID (H3BO3, E284)

Although it can cause kidney damage, boric acid is a mild antiseptic and is used to preserve urine samples. It has many other uses, such as in the manufacture of Pyrex,fibreglass and Silly Putty. It is a vital part of nuclear reactors because it controls and regulates the flow of neutrons.

BENZALKONIUM CHLORIDE

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Benzalkonium chloride is highly soluble in water and it has as its active centre a nitrogen atom that carries a positive charge. It can be used as a surfactant to help dissolve dirt but its main function here is to keep the eye wash free of microbes while also helping to remove them from the eyes.

GLYCERIN (aka glycerol, propane-1,2,3-triol, E422)

Glycerine is a by product from the manufacture of soap and biodiesel. It is also used in cough medicines and suppositories, and is added to liqueurs as a thickening agent. Here it helps to solubilise the molecules in the witch-hazel extract.

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WITCH HAZEL (aka Hamamelis)

A "natural" treatment for skin conditions, this extract strengthens proteincontaining tissue by tightening it. The polyphenols known as tannins are effective anti-inflammatory agents, and can also heal and stop bleeding. Tannins have anti-viral and antibacterial properties.

SODIUM BORATE (aka borax, E285)

This mineral occurs naturally in deserts and is used as a flux for soldering jewellery. Formerly it was the source of the perborate bleaches used in washing powders and it is excellent at removing stains from fabrics. Borax is used as a fertiliser, and is especially effective in olive groves.